The present invention relates generally to techniques that sense thermal stimuli. In particular, implementations employ thermometer elements or other thermal sensors connected by bridge circuitry into a bridge. Such bridges can be used, for example, in a calorimeter, a term used herein to refer to any device or apparatus that measures quantities of absorbed or evolved heat or determines specific heats; the use of a calorimeter is referred to herein as calorimetry.
Calorimetry can measure enthalpic changes, including enthalpic changes arising from reactions, phase changes, changes in molecular conformation, temperature variations, and other variations of interest that may occur for a particular specimen. By measuring enthalpic changes over a series of conditions, other thermodynamic variables may be deduced. For example, measurements of enthalpy as a function of temperature reveal the heat capacity of a specimen, and titrations of reacting components can be used to deduce the binding constant and effective stoichiometry for a reaction.
It is known to use bridges in calorimetry and other thermal sensing applications. For example, U.S. Pat. No. 3,467,501 describes a microcalorimeter in which a cell includes measuring thermistors mounted in a solid reactant zone and reference thermistors mounted in a block surrounding the cell; the resistances of the thermistors may be compared by connecting them into a Wheatstone bridge. U.S. Pat. Nos. 4,298,392; 5,312,587; 5,265,417; 5,451,371; and 6,701,774 describe other techniques in which thermistors, other temperature sensitive resistors, or other temperature sensing elements are in a Wheatstone bridge.
Previous techniques in thermal sensing with bridges have a number of limitations. It would be advantageous to have additional techniques for bridges that include thermometer elements or other thermal sensors. In particular, it would be advantageous to have techniques that could be used in very sensitive calorimetry.